Vol. 122, n. 2: 110 -120, 2017
© 2017 Firenze University Press http://www.fupress.com/ijae
ITALIAN JOU R NAL OF ANATOMY AN D EM B RYOLOGY
DOI: 10.13128/IJAE-21315 * Corresponding author. E-mail: kilicaslanfaruk@hotmail.com
Research article - Basic and applied anatomy
Prevalence of pedal symphalangism in Turkish
population. A radiographic survey
Selahattin Ozyurek1, Ozkan Kose2, Mustafa Celiktas3, Bogachan Tokatman2, Aziz Atik4, Omer
Faruk Kilicaslan2,*
1 LIV Ulus Hospital, Orthopaedics and Traumatology Department, Istanbul, Turkey
2 Antalya Education and Research Hospital, Orthopaedics and Traumatology Department, Antalya, Turkey 3 Ortopedia Private Hospital, Orthopaedics and Traumatology Department, Adana, Turkey
4 Balikesir University, Medical Faculty, Orthopaedics and Traumatology Department, Balikesir, Turkey Abstract
Objective: The purpose of this study is to investigate the prevalence of biphalengeal toes in
Turkish population and to analyze the differences between genders and symmetry patterns.
Material and methods: Bilateral foot radiographs of 279 subjects with a mean age of 40.7±16.3
(range, 18-78) years were reviewed to detect presence of pedal biphalangism. There were 146 (52.3%) female and 133 (47.7%) male subjects. Results: The overall prevalence of biphalangeal 3rd toe was 0.9%, 4th toe was 2.5% and 5th toe was 45.5%. The frequency of biphalangeal 3rd and 4th toe was statistically similar between genders (p=0.456 and p=0.163 respectively); however the biphalengeal 5th toe was more frequent in female subjects (p=0.004). In 138 (49.5%) subjects 5th toe was normal bilaterally. 113 (40.5%) subjects had bilateral 5th biphalangeal toe, and 28 (10.5%) subjects had biphalangeal 5th toe on one side (asymmetric pattern). 270 (96.8%) subjects had bilateral normal 4th toe, 5 (1.8%) subjects had bilateral biphalangeal 4th toe, and 4 subjects (1.4%) had asymmetric pattern. 276 (98.9%) subjects had bilateral normal 3rd toe, 2 (0.7%) had bilateral bipahangeal 3rd toe, and 1 subject (0.4%) had asymmetric pattern. The symmetric occurrence of biphalangeal toe in 3rd, 4th and 5th toes were equally distributed in both genders (p=0.061, p=0.227 and p=0.477 respectively). Conclusion: The present study represents the first report on the prevalence and distribution of biphalengeal toes in Turkish society. The prevalence of biphalengeal toes in Turkish population is considerably different from the Asian and Japanese population, but rather resembles European and North American populations.
Key words
Biphalangeal, fifth toe, epidemiology, Turkish population, symphalangism.
Introduction
The size of the lateral human toes presents a fairly regular mediolateral decrescent trend. This specific morphology of the human toes and decrease in size from medial to lateral has been interpreted as being related to the loss of plantar grip and bipedal-ism (Lessertisseur and Jouffroy, 1973).
The human foot has a big toe and four lateral toes. Anatomically it is known that the first toe is composed of two phalangeal bones (proximal and distal pha-lanxes) and the second to fifth toes (lesser toes) are composed of three phalangeal
bones (proximal, middle and distal phalanxes). Pedal symphalangism also called as ‘‘biphalangeal toes or two phalanged toes’’, refers to the fusion of two contigu-ous phalanges within the same digit, which is seen as end-to-end synarthrosis of the bones on radiographic examination (Figure 1). In other words, these toes lack distal interphalangeal joints. The pedal symphalangism was first described in 1492 by Leon-ardo da Vinci (O’Malley CD, 1952). Since the first description several other authors studied this anatomic variant. Although pedal symphalangism can be observed in the second through fifth toes, it is a relatively common anatomic variant that involves the fifth toe.
The incidence of pedal 5th toe in different ethnic populations has been reported
between 9.8 and 80.4%, with lower values being seen in Europeans and the highest rates in the Japanese population. However, to the best of our knowledge, there is no study investigating the prevalence of pedal symphalangism in the Turkish popula-tion up to date. The purpose of this study was to examine the plain anteroposterior radiographs of the feet in Turkish subjects in order to determine the prevalence of pedal symphalangism and their distribution. Furthermore, we analyzed the differenc-es between genders and symmetry patterns.
Material and methods
We retrospectively reviewed consecutive adult patients (>18 years of age, skele-tally mature) to whom bilateral foot radiographs were taken between January 2015 and January 2016 (12 months) for all possible indications, from picture archiving and
Figure 1 – (a) A triphangeal toe which has three phalanxes. (b) A biphalangeal toe in which the distal and
communication systems (PACS) and institutional clinical database of two hospitals. All subjects were patients admitted to either the emergency departments or ortho-pedic outpatient clinics. We excluded 54 patients, in whom the toes were not clearly depicted due to incorrect patient positioning making it impossible to judge about the presence of a biphalangeal toe, or all phalangeal bones of the foot were not demon-strated. Finally, bilateral foot radiographs of 279 patients (558 foot radiographs) were eligible and included in this study. This study was carried out in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amend-ments. Since this study was retrospective on radiographs taken for diagnostic pur-poses it was approved by default by Institutional board.
The presence of biphalangeal toes and their distribution from second through fifth toe was evaluated and recorded by two observers independently at separate times and any discrepancy was subsequently resolved by consensus. Data on patient age and sex were recorded from hospital records. Continuous variables were stated as mean and standard deviation and categorical variables as percentage and frequency distribution. The differences between the biphalangism at a particular location and the side and sex were analyzed using Pearson Chi-Square Test. A P-value < 0.05 was considered as statistically significant.
Results
A total of 279 subjects with a mean age of 40.7±16.3 (range, 18-78) years were analyzed. There were 146 (52.3%) female and 133 (47.7%) male subjects. No sub-jects had biphalangeal 2nd toe on either side. The overall prevalence of biphalangeal
3rd toe was 0.9%, 4th toe was 2.5%, and 5th toe was 45.5%. The overall distribution of biphalangism and their percentage incidence on each side is shown in Figure 2. The frequency of biphalangeal 3rd and 4th toe was statistically similar between
gen-ders (p=0.456 and p=0.163 respectively); however the biphalangeal 5th toe was more
frequent in female subjects (p=0.004) (Table 1).
In 138 (49.5%) subjects the 5th toe was normal bilaterally. 113 (40.5%) subjects had bilateral 5th biphalangeal toe (symmetric pattern), and 28 subjects (10.5%) had biphalangeal 5th toe on one side (asymmetric pattern). 270 (96.8%) subjects had bilat-eral normal 4th toe, 5 (1.8%) subjects had bilateral 4th biphalangeal toe (symmetric pat-tern), and 4 subjects (1.4%) had asymmetric pattern (Figure 3). 276 (98.9%) subjects had bilateral normal 3rd toe, 2 (0.7%) subjects had bilateral biphalangeal 3rd toe (sym-metric pattern), and 1 subject (0.4%) had asym(sym-metric pattern (Table 2). The sym(sym-metric occurrence of biphalangeal toe in 3rd, 4th and 5th toes were equally distributed in both gender (p=0.061, p=0.227 and p=0.477 respectively) (Table 3).
Table 1 – Prevalence of biphalangeal toe with respect to gender and side. P values are the results of Pearson
Chi-Square test. (Asterisk means significant p values).
Male Female Significance (p value) Right (n,%) Left(n,%) Right(n,%) Left(n,%) Right Left
3rd toe 2 (0.7%) 1(0.4%) 1(0.4%) 1(0.4%) 0,465 0,727
4th toe 4(1.4%) 5(1.8%) 2(0.7%) 3(1.1%) 0,299 0,311
5th toe 53(19.0%) 52(18.6%) 74(26.5%) 75(26.9%) 0,045* 0,026*
Table 2 – Symmetry patterns of biphalangeal toes.
3rd toe 4th toe 5th toe
Bilateral normal 276 (98.9%) 270 (96.8%) 138 (49.5%)
Bilateral biphalangeal 2 (0.7%) 5 (1.8%) 113 (40.5%)
Asymmetric 1 (0.4%) 4 (1.4%) 28 (10%)
Table 3 – Differences between male and female subjects with respect to symmetry patterns. p values are the
results of Pearson Chi-Square test.
Male Female
Significance (p value) Symmetric
(n,%) Asymmetric(n,%) Symmetric(n,%) Asymmetric(n,%)
3rd toe 132 (47.3%) 1 (0.4%) 146 (52.3%) 0 (0%) 0.477
4th toe 130 (46.6%) 3 (1.1%) 145 (52.0%) 1 (0.4%) 0.277
Discussion
This study investigated the prevalence of biphalangism in Turkish subjects. According to our results, the overall prevalence of pedal biphalangism in Turk-ish population was found to be 45.5% for the fifth toe, 2.5% for the fourth toe, and 0.9% for the third toe respectively. In other words, almost half of the population had biphalangeal 5th toe. The prevalence of biphalangeal 5th toe was statistically higher in female subjects. The symmetric distribution of biphalangeal digits was more frequent than asymmetric pattern.
Several radiographic and cadaveric studies have documented the prevalence of pedal biphalangism in different ethnic groups (Table 4). Although isolated cases of the absence of phalangeal secondary ossification centers have been published, the first quantitative data concerning the occurrence of the phalangeal secondary cent-ers in the lateral four toes was published by Venning (1956). Later on, Billman and Le Minor (2007) stated that the absence of one or more secondary ossification centers could be a derived pattern specific to the human species, like an autapomorphic pat-tern.
The overall prevalence of pedal biphalangism in Caucasian populations (Europe-an (Europe-and North Americ(Europe-an) has been reported between 35 (Europe-and 45%; on the other h(Europe-and, the overall prevalence of pedal biphalangism in Asian populations (Japanese, Indi-an, Korean) has been reported between 70 and 80% (Thompson and Chang, 1995). In a study of 2,550 European individuals, lateral toes presenting two rather than three phalanges (biphalangeal variants) were observed in 43.53% of the fifth toes, 2.51% of the fourth, 0.20% of the third, and 0.12% of the second toes (Le Minor, 1995). In the
Figure 3 – (a) A 34 year-old female patient with 3rd, 4th and 5th biphalangeal toes. (b) Lateral oblique
Table 4
– P
reviously r
epor
ted studies fif
th t
oe symphalang
ism (biphalangeal fif
th t oe). Author ,Y ear Sample Feet (n) Counting method Study type 2nd toe 3rd toe 4th toe 5th toe Pfitzner , 1896 German adults 838 Feet Cadaver 0,4 0,5 1,6 37 Hasselwander , 1903 Eur opean childr en/fetuses 172 Feet Cadaver _ _ 1,1 47,1 Adachi and Adac hi, 1905 Japanese adults 97 Feet Cadaver _ _ 3 80,4 Hasselwander , 1910 Eur opean childr en/adults 256 Feet Cadaver 0,8 1,2 4,3 41 Hasebe, 1912 Japanese adults 260 Feet Cadaver _ _ 7,7 73,5 Nakanishi, 1942 Japanese adults 500 Feet Radiograph _ 0,4 5,4 72,2 Tr olle, 1948 Danish fetuses 370 Feet Cadaver Venning, 1956 Eur opean childr en and adults 4632 Feet Radiograph 0,04 0,45 2,16 42,53 Asin, 1966 American adults 417 Individual feet Radiograph _ _ _ 47,5 Ellis et al. 1968 American adults 390 Individual feet Radiograph _ _ 0,8 48,2 Sandstr om and Hedman, 1971 Swedish childr en/adults 496 Feet Radiograph _ _ 1,2 34,5 W inlecki, 1978 American adults 974 Feet Radiograph _ _ _ 42,1 Carr oll et al., 1978 American adults 1324 Individual Feet Radiograph _ _ _ 33,8 Le Minor , 1995 Fr ench adults 2550 Individual Feet Radiograph 0,1 0,2 2,5 41,02 Nakashima, 1995 Japanese childr en/adults 488 Feet Radiograph 0 0,8 11,9 72,5 Park and Sohn, 1998 Kor ean adults 1187 Feet Radiograph _ _ _ 74 Geor ge , 2001
English old and young adults
204 Feet Radiograph _ _ _ 37,7 Chae et al., 2002 Kor ean adults 1290 Feet Radiograph 0,08 0,54 12,48 72,4 Case and Heilman, 2005 African-American Eur o-American Japanese skeletons 550 Feet Cadaver (c on tinued)
Author ,Y ear Sample Feet (n) Counting method Study type 2nd toe 3rd toe 4th toe 5th toe Rabi et al., 2005 South Indian 24(fetus) 112(childr en) 263(adult) Feet Radiograph Cadaver _ _ _ 87.5 (fetus) 9.8 (childr en) 11.8 (adults) Rozen et al., 2005 Australian adults 102 Feet Cadaver _ _ _ 26 Sohn et al., 2006 Kor ean childr en 50 Feet Radiograph Sohn et al., 2006 Kor ean adults 175 Feet Radiograph _ _ _ 74,29 Moulton et al, 2012 English adults 606 Feet Radiograph _ _ _ 44,4 Curr ent study , 2015 Turkish adults 558 Feet Radiograph _ 0,9 2,5 45,5 Table 4 – P reviously r epor
ted studies fif
th t
oe symphalang
ism (biphalangeal fif
th t
present study, our findings resemble the findings in Caucasian population rather than Asian populations.
In one study, no difference in the incidence between men and women was found (Le Minor, 1995), but others concluded that this variant is found more often in wom-en (Vwom-enning, 1960). Symptomatic problems of the forefoot predominate in womwom-en (Frey, 2000). In our study we found this deformity more frequent among women.
While some studies proposed biphalangism to be symmetric, conflicts may pre-sent. George (2001) stated that no difference exists in the percentage of biphalanged 5th toes between left and right foot. Ellis et al. (1968) showed that the patients in whom both feet had been radiographically assesed were either biphalanged or triphalanged on both sides. Moulton et al. (2012) showed a small number of subjects (4.8%) who had different numbers of phalanges in either foot.
Currently there are two different theories about the occurrence of biphalangism. It may be the result of incomplete segmentation, with failure of development of the distal interphalangeal joint during gestational life (Billmann and Le Minor, 2007). Most commonly it is believed that the biphalangeal fifth toe is caused by a pathologic fusion of the middle and distal phalanxes during postnatal life, attributable to trauma or disuse of this joint (Le Minor, 1995).
Dereymaeker and van der Broek (2006) searched for the prevalence of a biphalan-geal fifth toe in patients with hammer or claw toe, bunionettes, and overriding fifth toe. They only found statistically difference in hammer or claw toes, in which the prevalence was significantly higher than the control group. So they concluded that the stiffness and rigidity of the biphalangeal fifth toe may predispose it for sympto-matic hammer or claw toe. A biphalangeal fifth toe is stiffer and less able to
accom-Figure4 – A 22 year-old male patient with fracture biphalangeal left fifth toe, which was misdiagnosed as
modate the pressure of conventional shoe wear. Likely, Thompson and Chang (1995) have suggested that surgery on the fifth toe is more common in toes with two rather than three phalanges.
With loss of flexibility created by this synostosis, it is often more difficult for the digit to accommodate irritation from shoes and this therefore predisposes the fifth toe to the development of painful pressure keratoses or nail dystrophy (Banks et al., 2001). Kiati-sevi et al. (2011) described a giant cell tumor at the distal phalanx of the biphalangeal fifth toe, where it is very rare to find. But they couldn’t conclude that biphalangism may have been a reason. Furthermore in context of trauma and fracture biphalangism may be misdiagnosed. But trauma can be easily distinguished from pedal symphalangism because traumatic fusion nearly always results in flexion, mediolateral deviation, or rotation of one phalanx relative to the other, while in pedal symphalangism the com-bined phalanges will be quite straight (Case and Heilman, 2005; Figure 4).
The present study has some specific strengths. This is the largest series of foot radiographs examined in the current literature in adults. All the radiographs were digital, thus observers could subjectively adjust the display parameters such as con-trast, opacity and brightness on the computer screen. This provided a correct identi-fication of all biphalangeal toes. Digital radiography examination is a useful method for determining skeletal ossification and is also simple, objective, fast and relatively inexpensive (Burdan et al., 2002; Rabi et al., 2005). Furthermore, two independent observers reviewed all cases to decrease the errors. Additionally, we could be able to examine the symmetry patterns, as bilateral radiographs were taken.
As a conclusion, the present study represents the first report on the prevalence and distribution of biphalangeal toes in Turkish subjects. The prevalence of pedal biphalangism in Turkish population is considerably high, and it resembles the Euro-pean population.
Conflict of interest
The authors have no conflict of interest to declare. References
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